In the prior art such as a CT scanning device, scan imaging of an object using X-ray has been widely used. Traditional X-ray scan imaging generally makes use of attenuation characteristics of the detected material to X-ray so as to examine the internal structure of the object in a nondestructive way. If the structural constitutions of respective parts inside the object are notably different in density, the effect of the traditional X-ray imaging technology is especially significant. As for substances consisting of light elements, they are weak-absorbing substances for X-ray, thus the internal specific structures thereof almost cannot be seen by means of the traditional X-ray imaging technology. It is also difficult to obtain a clear image even if other auxiliary means are used, such as injecting contrast agent into biological tissues, which results in a lot of imperfections. In the 1990s appeared an X-ray phase-contrast imaging technology. Said phase-contrast imaging is to observe change in the electron density inside an object by capturing phase-shift information of X-ray, thereby revealing the internal structure of the object. At the beginning, the appeared phase-contrast imaging methods usually enhance the low contrast resolution of the radiated image by using interference or diffraction phenomenon of coherent or partially coherent X-ray. On such a basis, in the patent applications CN200810166472.9 “System and method for X-ray gratings phase-contrast imaging” and CN200810224362.3 “X ray Phase contrast tomographic imaging”, wherein all the contents of said patent applications are incorporated into the present application by reference, HUANG Zhifeng et al. put forward a novel technical concept and solution of non-coherent grating phase-contrast imaging, including: two absorption gratings are used to relatively move several steps in parallel in one grating period, the detector acquires one image at each step; after the acquisition process in one grating period has been finished, the information of the refracted image of the object to be detected is calculated by comparing the sample light intensity curve to which each pixel point corresponds with the background light intensity curve. This leads to a good phase-contrast imaging effect. Said method can be operated under multicolor, non-coherent ray sources to implement simple and feasible means.
In addition, during the progress of the X-ray imaging technology, there also appeared a dark-field imaging technology. Said dark-field imaging is a technology of imaging substance materials by using non-direct light such as scattered light, diffracted light, refracted light, fluorescent light, and the like, and imaging the internal structures of the substances by means of the difference in their capabilities of scattering X-ray. As for the dark-field imaging, due to the unique optical properties of hard X-ray, it is very difficult to produce the required optical elements, thus the hard X-ray dark-field imaging is always hard to achieve well. However, the hard X-ray dark-field imaging technology possesses particular advantages in the capabilities of distinguishing and detecting the microstructures insides the substances over the bright-field imaging and the phase-contrast imaging. Since scattering of the hard X-ray is of a micron-magnitude or even nanometer-magnitude, the hard X-ray dark-field imaging technology is able to see the ultrastructures inside the substances which cannot be distinguished in the hard X-ray bright-field imaging and phase-contrast imaging. Wherein in the patent application in 2009, CN200910088662.8 “X-ray dark-field imaging system and method”, wherein all the contents of said patent application are incorporated into the present application by reference, HUANG Zhifeng et al. put forward a technical solution of performing dark-field imaging of an object by using X-ray, including: emitting X-ray to an object to be detected; enabling one of the two absorption gratings to perform stepping in at least one period; at each stepping step, the detector receiving X-ray and converting it into an electrical signal; after at least one period of stepping, the X-ray intensity at each pixel point on the detector is represented as a light intensity curve; calculating a secondary moment of the scattering angle distribution of each pixel according to the contrast between the light intensity curve at each pixel on the detector and the light intensity curve in the absence of the object to be detected; taking images of the object from different angles, and then obtaining a scattering information image of the object according to a CT reconstruction algorithm.
The grating imaging technologies as stated above all need to measure a light intensity curve of each detection unit (pixel point) on the detector by using the stepping technology, wherein the basic principle for the stepping technology is: after a source grating is fixed adjacently to an X-ray machine source, in the technology based on a Talbot-Lau interference method, a phase grating or parse grating relatively moves several steps in parallel in one grating period; however, in the technology based on a classic optical method, two absorption gratings relatively move several steps in parallel in one grating period. The detector acquires one image at each step. After finishing the acquisition process in one grating period, the refraction image information, attenuation image information and dark-field image information can be calculated by comparing the sample light intensity curve to which each pixel point corresponds with the background light intensity curve. Since the phase grating, parse grating or absorption grating has a period of a several-micron magnitude, and a stepping precision of a submicron-magnitude is required, which highly requires the precision of a mechanical device, the shock-proof of the integral device, and the environmental temperature, and the difficulty in constructing the imaging system and cost therefore extremely increases, thereby limiting application and extension of such a novel grating imaging technology.